"Plastic does not degrade, it lasts for half a millennium. Every minute there's a truckload of plastic waste entering the ocean.

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Video:Theresa May's 25-year plan to clean up Britain

"It's ubiquitous, it's in everything, it's in up to 50% of what the average supermarket sells. The time to act is now.

"Take our ready meals. They are in a board carton sleeve which is good, made of paper, but the problem is the black plastic tray.

"We're going to replace that with a wooden board tray, and the final piece of the jigsaw is the plastic film over the top: we're looking at cellulose-based technologies which are made from paper pulp."

Some within the plastics industry think it's a step too far and are questioning how "green" the move really is.

Image:The plastic packaging, versus the new pulp alternative

"It's a really surprising announcement", Barry Turner from the British Plastics Federation said. "The reason a lot of supermarkets embraced plastics packaging is because it's resource efficient.

He claimed: "If they move away from plastics in the way that they've declared, it will mean that the weight of the packaging they use will increase four times, the carbon emissions will increase by around three times, the amount of energy to make that packaging will increase two-fold.

"So, the net result is that the environmental footprint of the packaging that they're including, will increase."

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Video:Plastic pollution found seven miles under sea

According to Plastics Oceans Foundation an estimated eight million tonnes of plastic enters the world's oceans every year, putting all forms of marine life at risk.

Campaigns like Sky Ocean Rescue are changing the way consumers are thinking about plastic.

Iceland said a survey of 5,000 shoppers found that 91% would be more likely to encourage friends and family to shop there if they pursued a plastic-free future.

The chain isn't the biggest player within its industry - its market share is just 2%. But, it's hoping customers buy into it, like they do at zero-waste food shop Hetu in Battersea, albeit on a much smaller scale.

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Video:Sky News Special Report: Our Ocean

"My business plan is to be out of business in five years," said Laura Boyes who set up the store six weeks ago.

"I want a big organisation to do a shop like this, fully plastic-free, and do it on a large scale where you can pass savings on to the customers and know the supply chains, and do it from a wholesale point of view."

While Iceland welcomes the Prime Minister's call for "plastic-free aisles", it points out that it has been working on this for a year, and it's convinced it's the way forward.